Electrostatic charge is the result of electrification of an object such that the charge is confined to the object. Friction between two surfaces in close contact typically gives rise to electrostatic charge or static electricity.
Textiles and plastics generally have low conductivity and dissipate charge at a relatively low rate. While it has been proposed to attenuate electrostatic charge build-up on textile and plastic materials by reducing its rate of generation, friction is inherent in many plastics and textile processing operations, particularly the latter, and cannot be substantially reduced. Consequently, increasing the rate of electrostatic charge dissipation of a textile or plastic material by increasing its electrolytic conductivity through the application of internal or external antistatic agents is commonly used as a means of controlling electrostatic build-up in such materials.
External or surface antistatic agents are directly applied as a coating to the surface layer of a textile or formed plastic substrate, typically dissolved or suspended in a suitable vehicle, such as water or another solvent. Internal antistatic agents are commonly used in formed plastic substrates and are physically mixed or blended with the resin mass prior to the forming operation, e.g., spinning, drawing, molding or the like, so as to be uniformly distributed throughout the body of the finished product, including the surface layer. Internal antistatic agents generally provide a longer lasting electrostatic charge dissipative effect.
Various chemicals have been proposed for use as antistatic agents, including, by way of example, long-chain amines, amides and quaternary ammonium salts; esters of fatty acids and their derivatives; sulfonic acids and alkyl aryl sulfonates; polyoxyethylene derivatives; polyglycols and their derivatives; polyhydric alcohols and their derivatives; and phosphoric acid derivatives.
Treatment of polyester and nylon fabrics with antistatic agents has been shown to reduce soiling. Static-prone plastic articles, such as packaging materials, that are treated with antistatic agents resist accumulation of dust and thus are more attractive for packaging of consumer products. Moreover, static charged plastic packaging and other plastic products have the potential to cause damage to semiconductor chips and constitute a possible explosion hazard in areas where flammable gases are used.
Ideally, surface antistatic agents used in textile and plastics processing are stable and not transient. That is to say, an amount of antistatic agent sufficient to provide effective electrostatic charge dissipation is retained on the surface of the coated substrate, whether textile or plastic, until processing is complete. Such processing often involves exposure of the treated textile or plastic to an aqueous environment, which tends to reduce the amount of antistatic agent present on the treated surface, thus diminishing its static dissipative effect. The use of stable antistatic agents offers the advantage of obviating repeated application of the antistatic agent to the static-prone substrate during processing.
Antistatic agents are also used for enhancing the receptivity of plastic surfaces to electrostatically applied coatings, e.g., in automobile production. See, for example, U.S. Pat. No. 5,219,493. In this application also, it is desirable that the antistatic agent resists removal when exposed to an aqueous rinse or wash liquid.